Chapter 9, Problem 27E

Hand dexterity Researchers studied the dexterity of children using a timed test called the Functional Dexterity Test (FDT). Of course, they needed to allow for differences in dexterity between their subjects’ dominant and non-dominant hands. Here is a scatterplot of the speed at which subjects completed the task vs. their age, and lines for dominant and nondominant hands:

Here is a corresponding regression. The variable Dominant is 1 for trials in which a child used his or her dominant hand and 0 for trials with the non-dominant hand. Speed is recorded in tasks/second.

Response variable is: Speed

R-squared = 64.2% s = 0.4171

1. a) What is the proper interpretation of the predictor Dominant in this regression?
2. b) Are the conditions required for using an indicator variable met for these data? Explain.